A number of methods are available for applying subtitles and translations to existing movie films, and these can be grouped into three main groups:
(a) photographic negative title systems based on the use of a negative animation camera loaded with a high contrast film;
(b) application of the desired script by means of a lettering set applied by heat; this method involves the use of heat and of a chemical etching treatment of the film to soften the emulsion prior to the application of the script by a stamping process.
(c) application of heat and etching as in (b), but using a coating of wax on the film, stamping the text on the wax and etching the revealed emulsion of the film to form the desired characters.
System (a) is the most expensive one. A separate high contrast transparency or film is used having the same length as the movie film. The added film is superimposed on the existing one and bears the required titles and lettering. This method is highly complex involving making one or more negatives of the superimposed subtitle and actual file transparency. This method is economically feasible only when a large number of films is to be produced.
System (b) comprises preparing a separate film bearing the desired titles, preparing from the film reduced-size copper or zinc casts of the size to be applied to the cinematic film, softening the emulsion of the cinematic film, stamping the film in a special device by means of the heated cast letters, and advancing intermittently frame after frame so as to apply to the required number of frames the same title and changing the other titles as the film is advanced, as required.
On the average, a cinema film has about 600 to 1000 such printed lines. Each printed line has to be reproduced on a number of frames to be perceptible and readable by the human eye. After applying all the required printed lines, the film is subjected to another treatment for hardening the emulsion. As a rather large number of different cast molds is required, errors are likely to occur, for example in the synchronization of the cast and film frame, or in the sequence of the subtitles. In addition, after application to a number of frames, the cast letters tend to become less sharp, and unclear lettering results due to accumulation of debris.
System (c) is similar to system (b), but wax coating is applied to the film and the lines are imprinted on this layer. These lines thus remain sharp but become wavy After the stamping process, the film is subjected to a special treatment which etches the exposed locations of the surface, thus resulting in a sharp print of the required lines, after which the wax layer is removed in another solution. This method is more expensive, and it has the inherent danger of etching the film too much if the wax coating does not have exactly the required thickness and uniformity.